Learn React.
Understand rendering, state ownership, hooks, and performance.
React essentials
Start with the essentials or pick the concept you need.
01Rendering & stateExplore concepts
02HooksExplore concepts
03State & performanceExplore concepts
What you will study in React
Focused lessons organized by concept. Start with the explanation, trace the examples, and check your recall before moving on.
Rendering & state
Props are values a parent supplies to a component, while state is data React remembers for a component across renders. Both influence the UI, but a component should not change its received props directly. State updates request a new render so the screen can reflect the new data.
Hooks
useEffect synchronizes a committed component with something outside React, such as a connection, timer or browser event listener. Its setup runs when relevant dependencies change, and cleanup ends the old synchronization. Effects are not the usual place to compute values already available during rendering.
State & performance
Local state belongs to a nearby component, a client store coordinates shared UI data, and server state represents data owned by a remote service. Server-state tools manage freshness, fetching and invalidation because the browser is only keeping a cached copy. Choosing the owner first prevents duplicated and conflicting sources of truth.